The subject invention relates generally to gasification systems and processes, such as those used in Integrated Gasification Combined Cycle (IGCC) power generation. More particularly, the subject invention relates to fuel feed apparatus and methods for a gasification system.
Gasification is a process for the production of power, chemicals, and industrial gases from carbonaceous or hydrocarbon feedstocks such as coal, heavy oil, and petroleum coke. Gasification converts carbonaceous or hydrocarbon feedstocks into synthesis gas, also known as syngas, comprising primarily hydrogen and carbon monoxide. The resultant syngas is a feedstock for making useful organic compounds or can be used as a clean fuel to produce power.
In a typical gasification plant having a dry solids feed system, the feedstock, such as coal, is introduced to a grinder where it is ground into solids particles of a predetermined size. While the grinding process produces solids particles of the predetermined size, a quantity of smaller particles, known as fines, are also produced by the grinding operation. Before feeding the solids and fines into the gasifier, the solids and fines are typically dried to eliminate surface moisture for reliable flow and increase efficiency of the gasification process. Smaller particles in the feed stream such as fines, however, are capable of collecting large amounts of surface moisture thereby increasing the amount of drying required to maintain reliable flow. Further, the low mass of the fines particles reduces the feed rate capability when gravity fed from a hopper and when feeding into other equipment upstream of the gasifier. Also, a high fines content in the feed stream increases the potential for effluent emissions from the gasification process and the potential for dust explosions when stored and handled upstream of the gasifier.